Compensator valve



March 27, 1951 E. A. ROCKWELL 2,546,677

COMPENSATOR VALVE Original Filed April 11, 1941 4 Sheets-Shet 1 INVENTOR X a QM March 27, 1951 Original Filed April 11, 1941 E. A. ROCKWELL COMPENSATOR VALVE 4 Sheets-Sheet 2 INVENTOR A'lTORN March 27, 1951 E. A. ROCKWELL COMPENSATOR VALVE Original Filed April 11, 1941 4 Sheets-Sheet 5 YA. mrll S INVENTOR QWQ A'ITORN 3 a n m March 27, 1951 E. A. ROCKWELL COMPENSATOR VALVE 4 Sheets-Sheet 4 Original Filed April 11 1941 C Y m m M 4 w T 7 7 N O 9 1 8. 5; 7 W9 .m A W 9 Q 3 Y 8 4 w @9 m 8 v .w W m w% 1 H 5 0 7 7 w fink Patented Mar. 27, 1951 UNITED STATES PATENT. OFFICE- COMPENSATOR VALVE Edward A- Rockw ll, Clev land; O io Application February 17, l943', Serial No; 176,2515, which is a division of application Serial No. 388,003, April 11, 1941. plioation-Octobe'r- 28, 1944', Serial No. 560,864

9 Claims. (Cl. 137-153) The objector my invention is to provi e a valve m ans for oompen ationor m h nn. nd which may for example, be applied a p ls tor ystem oi'anydeslr d haraoter, as for in tance in connection wi h pow r units such as h se. above roferredto. One of h obj cts of my inven on, furthermor m nt th l q i ompensatln or transfer valve on the valve operating means wh h con rols the fluid pres ure i let f r the power unit. Another objectis to arrange the apparatusso as to enable the transf r valve to be located adjacent to the operating cylinders soas to avoid long tubing and air bleederg as far as possible. Further objects of my invention will appear from'the detailed description of the same hereinafter.

While my invention i capable of embodimen in manydifferent forms, for the purpose of illus tration I have shown only one form thereof in he acoompanyinedraw n s in which Fig. 1 is a perspective view showing the parts of an automobile-chassis to which my invention isapplied;

Fig. 2' is an levation partly .in ection f a master cylinder used in aocordanoe therewith;

Fig. 3 is a plan view of-a power unit madein accordance withmy invention, withthe air filter removed;

Fig. 4 is an end elevation of the same;

Fig. 5 isa longitudinals tionthereof tak on line 5--5 of. Fig- Fig. 6 is a vertical section taken on line 6.6 of Fig. .5 showing the relative location, of s the valveeoperating lever and diaphragm valves operated thereby;

Fig. 71 a detailed section showing the mounting of said valve-operatin lever taken on line 1-1! of Fig. 6; and

Fi 8 is a vertical section of a modifie air in: let-device.

Referring o h drawings, 1 have shown a pedal I mounted on a 'fixedpivot 3 at any .cles

Divided and this apt.

sired point omen-au omobi e chass s not'sholwm which has an. p rat ng nk 4 atta h d to an nodal, whi h in turn is conn c ed to an operating lever 5 of; a master cylind r 6. Th maste cyl' nn r 6 may be constr cted in. a o dance with.

any desired tyn i mas er yl nder but may, i017 xa ple. he oonst -uoted n ao ord e wit the master cyl d r sho in the. L'cu head atent 397,063; granted, M ren-2o. 1939. Theooer atin le er 5 may be mounted no sha t'l which xtends into saidmaster cyl nd r, and on said.

shaft 1 within s id maste oylinder 6 there is.

an operating 8 whioh bears upon a piston 9 that ex ends into a o linder 10 which is'in. oommunlcation-with the liquid n the master cyl nder shy moens f a port H. which port I is on covered in the retracted. position of t e pistont. The sa d. master cy inder 6 thus a ts as a s orage, hambe for he, hydrauli liquid and s provided with cover .lZ- having a vent 3, said c ver havin the usual removable filler cap l4. The y nder 10 has the u ual spring is for tracting he piston Send. a flexible discharge c nduit 16;

which leads to a screw-thr aded fitting Boon a; power unit IL-sa q power'onit l1 having'a flexi-i ble discharge pipe 18 whichleads. by any desired braneh pipe to wheelcylinders [9 loc ted on the four wheels of the automobile chass s not shown.) o as to perate th'e'usual rok sho to and provided in'conne tion w th. a l of; said.

' Wheels .for c operating. with, brake droms not shown.) thereon. e saidnipe'lt is co ne ted bye so w threaded fit hgztto a plunge o s-' ing 25. oithe nowerunit said housi g having pr ject ons 26 and?! carrying tud 28 nd 2t s wen as nut 0' and 3| to h ld i pla e'tig tly clamping members 3 andta which a a rang d to he clamped around a steer ng oo um 't lot the automobi e .chjaissist Also secur d t sa d plun er hou in 'thereiisl a rear sh l secured in place by screws 36; The saidr ar s ell; y means of screws 3?, lamps in place a m n diaphragm '38against a forward shel 39 which has a sicr w threaded sleeve secured ther to and wh ch oommiunicates by fitt ng 4| with a flexible n ne 42 which leads to a ma ifold 430i he internal combustion engine mou ed o sa d chassis i r driving the aut m b e- Th sle vo contains a checkal e 43o prwideo with p ripheral notches 43b and having a y ndri al: valve seat 439 cooperating the ewith.

he liqu d for ed ann ll ut of the master cylinder fiend reoelv. by the power nni 'li tr the p pe 5.-ent rs t r u h a'oo pling inl m 4 4 insa d-plo serhonsine 251nto a'valve ,7

her 45. This chamber 45 has a peripheral recess 45a into which there is sprung a liquid distributer plate 455 having near the edge thereof a marginally arranged series of notches 450 to distribute the force of the incoming liquid, thus avoiding undesirable impact on the inlet valve. The initial operation of the brakes by the manual force applied, causes the liquid to fiow into a chamber 46 in a plunger 41 having ports 48 leading to a cylindrical chamber 49. The plunger 41 has a U-shaped rubber seal 50 and carries within the same a valve stem i having a head 52 thereon provided with an internal annular recess, having a cylindrical rim, beneath which there is a rubber gasket 53 restrained by said rim arranged to act as a compensating inlet valve, the seat for which is a shoulder 54 on the. plunger 41, so that when thus seated the hydraulic liquid, which in the initial operation of the apparatus is conveyed from the cylinder 49 by a port 55 to apressure cylinder 56 and thence to the brakes through the pipe I8, is cut ofi by said valve 53, 54 so as thereafter to apply the power from the power unit. It will be noted that the valve stem 5! serves as a supporting guide for the plunger 41 which is reciprocable to some extent on said valve stem. The movement of the plunger 41 to the right, in Fig. 5, is limited by a stop 51 formed on the interior of the coupling 44 and the movement of said plunger 41 to the left of said figure is limited by a plunger sleeve 58 which'is screw-threaded on the saidstem 5 I. i

' The plunger sleeve 58 has thereon a plunger 59 and an annular rubber seal 60. The said plunger 59 operates in a cylindrical chamber H which carries a coil spring 62 normally, forcing the plunger 59 to the right so as to unseat the valve 53, 54, which when open compensates the liquid on the two sides of the valve. The other end of said spring 62 rests against a sleeve '63 located tightlyi'n the .end of the chamber 6 I, said sleeve having a cap ring 64 and a leather gasket 65 around a rod-shaped plunger 66 carried within a bushing 61 within the sleeve 63. The said rod-like plunger 66 bears at its rear end against the plunger 59 and .at its forward end bears against the endof'a valve-operating lever 68, which in turn operates a spring 69 located around a guide rod having a screw-threaded reduced end 1I passing through plates 12 and 13 on the diaphragm 38 around anopening 14, where it is held in place by a nut15. The plates 12 and 13 are secured together by screws 13a at the periphery thereof and screws 131) located on opposite sides of a laterally ofiset portion 130 of the plate 12. The said lever 68 is supported by a pivot 16, which can be placed at any desired point along said lever toobtain the desired lever ratio, 'on a rod 11 having a screw-threaded end 18 passing through the plate 13 to which it is tightly held by a nut 19. The other end of the lever 68 has a pivot 80, by means of which it is pivotally connected to a valve-operating sleeve 8I screw-threaded on a valve stem 82 having a vacuum or outlet valve head 83 connected thereto and which carries within the same a rubber washer 84. The said rubber washer seats upon an annular valve seat 85 which is clamped to a subsidiary diaphragm 86 supported by screws 81 and a clamping ring 88 from the plate 12. This clamping to the diaphragm 86 is accomplished by means of a clamping plate 89held in place by a valve sleeve 90 screw-threaded to the annular valve seat 85. A coil spring 9| bears at one end against the clamping plate 89 and at the other end against the plate 13 so as to normally force the valve sleeve to the left of Fig. 5 and thus seat a rubber washer 92 of an air valve or inlet valve 93 against an annular valve seat 94 carried in the plate 13. It will be noted that the valve sleeve 96 has air ports 95 leading from within the sleeve to the interior .of the shell 35. The air which is admitted to the interior of the shell 35 through the valve 94 is received from opening 96 communicating with a chamber 91 between the plates 12 and 13, said openings 96 being provided in a screw-threaded plug 98, having a leather gasket 98a, passing through the plates 12 and 13. A hollow plunger 99 is screw-threaded to the plug 98 and has a central passageway I69 communicating with a longitudinal passageway IOI in the plug 98. This hollow plunger 99 clamps the plate 13 against a shoulder I02 on the said plug 98. Ports I03 in the said plunger 99 communicate with a chamber I04 in the said plunger housing 25 which has an air vent I05 leading to the outer airthrough a tube I051; leading to an air filter casing I051), filled with horse-hair, having a headed sleeve I050, with openings I05d, screw-threaded to the tube I65a and provided with a shoulder I95e against which a plate I051 rests, which has air vent openings g. The chamber 61 is also connected to said vent I05 by a passageway I96 located between the chambers 6| and I04. The

said chamber I94 has a screw plug I01 which merely fills an opening I08 used for convenience in drilling the passageway I03. Furthermore, the said chamber I04 has a bushing I09 and outside the same a sleeve H0, which is tightly carried within the chamber 594. Theend of the sleeve [I6 is screw-threaded to a cap III which acts as a stop in the movement of the plate 13 and also serves to hold in position a leather seal II2 against the outside of the hollow plunger 99.' Within the hollow plunger 99 there is a rod II3,'

operating in an air transfer passage II3a, the rear end of which rod is screw-threaded into a plug H4 acting as a closure for the cylindrical chamber 56. On the forward end of said rod II3 there is a head H5 holding in place the spring I I1, the other end of said spring I I1 being supported against a headed sleeve H8 which in turn rests against a shoulder H9 in the hollow plunger 99. The said headed sleeve II8 carries a washer I I91: and, furthermore, is screw-threaded to a plunger stem I26 passing through a guiding sleeve I2I held in place in the chamber 56 by a screw I22. The said plunger I20 carries rubber seals I23 and I24 between which there is carried a coil spring on the plunger stern l20, which in turn has a plunger head I26 adjacent to the rubber seal i24, which exerts a pull induced by the diaphragm 38 to place the liquid in the chamber 56 under increased pressure due to the relative sizes of the diaphragm 38 and the plunger I26.

In assembling the power unit it will be understood that the diaphragm 38, plates 12 and 13 and the valve elements together with the operating lever 68 mounted thereon, can be made into one assembly and the plunger mechanism made into another assembly and that these two assemblies can then be assembled together While at the same time securing the shells 35 and 39 thereto.

In Fig. 8 I have shown a modified air inlet device in which there is provided means for adjusting the amount of air admitted at different altitudes at which the automobile is operated and so as to control the outlet pressure of the apparatus;-

gamma- Inthis 'figur'e I have shown connected to the air vent port I05 a screw-threaded tube I21 havinga flared portion I28 provided with a flange I29 against which there is clamped a rubber diaphragm I30, having a central aperture I3I, by means of screws I32 passing through the diaphragm into said flange I29'and passing through a flange I33 on an air valve housing I34 provided with air ports I35. The upper portion of the housing I34 has a screw-threaded opening I36 through which there is arranged to pass an adjusting screw I3'I provided with a knurled head I38. On the screw I 3-1 there is a lock-nut I39'so as to hold in place above the housing I34, an air filter shell I40 filled with horse hair and which has a depending rim I4I so arranged as to leave an annular air inlet I42 between the same and the flanges I29 and I33. The adjusting screw I3! has'a round-lowerend I43 which is received in arecess I44 in an air valve plate I45 having a downwardly directed rim I46, the air valve plate I45 beingpressed upwardly by a compressed spring I4'I which is supported at its lower endon ashoulder I48 Within the tube I21. The rim- I48 is arranged to be adjusted into'or out of contact with-the diaphragm I soas to provide an air passageway I49 between thevalve plate I45 and said'diaphragm I30. The diaphragm I30 is sup-. ported in its uppermost positionby a supporting ring I50 which is dished upwardly so as to receive a coil spring I5I seated at its lower end on.

a shoulder I52 in the inside of the-flared portion I28 of the tube I21. mobile at high altitudes thespring I5i willbe in itsposition of full extension with the plate I45 adjusted out of contact with the diaphragm I}, whereas at lower altitudes or where the output pressure applied to the-brakes is to be lessened, the plate I will be adjusted into contact with thediaphragm I30 so as to-compress the spring I5I more or less, as desired, according tothe position of the screw I31.

In the operationof the apparatus, when it is desired to apply the brakesthe-pedal I is moved tothe left, in Fig. 1, whereupon some of the liquid from the master cylinder 3 passes from the pipe I6 through the valve chamber 45, ports 48,

port 55, chamber 56 and pipe I8 to the wheel brake cylinders I9 so as to move the brake shoes 20"a'nd 2| up into position, for applying the main braking'effec't. A further increaseof this manual pressure from the pipe IE will cause the piston 5t to move forwardly in the chamber 6|, thus closing the valve 53, 54 due to the back pressure-on.

the plunger 41 and the compressibility of the rubber ring 53 and simultaneously operating the lever 68 so as tomove the valve 83 into closed position while moving forwardly, slightly, the plates I2 and 13 as well as the diaphragm 38 through the intermediary of-the spring 69. Furtrier-increase of the manual pressure, resulting in further movement ofthe plunger rod es in this direction, results in openingthe air inlet valve 93' When operating the auto said valve 93 and thediaphragm 86 so as'to prvent the valve 93 from being suddenly openedby said-incoming air. It-will be noted, furthermore,

that the air may be admitted, in this way, to thechamber within the shell 35 in any desired-inferred to, tending to move the diaphragm 83- downwardly in Fig. '7 many one position of power application in which the pedal I is held. Inother words, as the diaphragm 38 moves-to the left, in

Fig. 5, the pivot, l6-is carried thereby, and upon cessation of movement of the pedal I, while the valve 93 is still open, thediaphragm 38 will still continue to'move tothe left slightly as the left hand end of the plunger 65 is then a stationary pivot. At this time, also, a slight movement ofthe lever 68 affects the valves 83 and 93, to move them into lapped position. Consequently, the

said valves can apply amodulateddegree of pres-- sure to the right side of the diaphragm 38, as de sired. Similarly, the air may be withdrawn by increments in the same manner from the right of thediaphragm 38 through the opening of the valve 83 to the desired extent for this purpose,

by lessening the pressure exerted onthe pedal I.

When the atmospheric air pressure has been ad-- mitted to the desired extent to the right of the diaphram 38, this actionwillbe accompanied bythe movement of the hollow. plunger 09- to the left in Fig. 5, against the compression of the spring I I? so that the-plunger'head I26 willmovei pipe I8 to the brakes and exerting the reaction from the chamber 56 and 49011 the foot through the pedal I. This pressure exerted on the brakes may be of any desired maximum but may, for example, be about 1500- lbs. per square inch, whereas the, manualpressure applied from the master cylinder may, for. example, be from 0 to 600 lbs. per square inch, or any other ratio of these or other pressurescanbe obtained, as'desired. In view of the fact that liquid from the master cylinder is directly connected to and takes:

moved only by the air pressure acting on the diaphragm 38. Because of this arrangement, in which the foot always performs apart of the work by supplying part of the liquid used in applying the brakes,even when the power is being applied about 40% of the liquid in applying the brakes is provided by the foot pressure. This is owing to the fact that the volume received inthe right hand endof the bore in which the'plunger slides is smaller than the volume delivered by the pipe I 8, thus providing for a small pedal travel. In fact, at times the foot pressure applied to the brakes can be increased without-substantially moving the foot forwardly. Thus, an

effective modulation of the pressures applied to in this power unit, whatever force is supplied 7 manually by the foot pedal I-is entirely offset by an equal and opposite force from the power piston I20 so that, consequently, all the brake,- applying force for operating the brakes, when the power is on, is derived entirely from the power plunger I20. This apparatus is thus a full power unit. For these reasons, also, the brake is practically as efiective, irrespective of considerable variations in the vacuum from the manifold, due to the direct connection just referred to and the large size of the diaphragm 38. Furthermore, it will be noted that at all times a reaction passes from the liquid applied to the operation of the brakes back to the foot, through the pipe I3 either from the liquid in the chamber #39 through the valve 53, 54 when this valve is open, or from the chamber 49 on the plunger 41 when said valve is closed, thereby making the degree of applica-,

tion of the brakes readily ascertainable without the pedal being moved towards its off position. Also, the actuation of the brakes is made more efiective by reason of thecoordination of the travel of the pedal I to the movement of the brakes, as it will be evident that the movement of the brake liquid is coordinated to the travel of the liquid supplied from the master cylinder. In order to throw the brakes out of operation, the manual pressure on the pedal is fully released, whereupon the spring 69 opens the valve 33 and allows the valve 93 to close and the springs II? and I25 withdraw the diaphragm 38 to the right, thus admitting vacuum thence through the ports 95 to the right of the diaphragm 38. This action is accompanied by the unseating of the valve 53, 54, thus restoring the parts again to their original positions and compensating for any possible loss of liquid in the power unit, ready for the application of the brakes as desired.

In the modified form of air inlet apparatus as shown in Fig. 8, the adjusting screw I3? is arranged to adjust the air inlet plate M to any desired position according to the altitude at which the automobile is operating or according to'the amount of the maximum output pressure desired to be applied to the brakes. In other words, when the automobile is operating at a high altitude, with consequent lessened atmospheric pressure, the plate I45 will be adjusted upwardly to a position away from contact with the diaphragm I30. When, however, the automobile is operating at a lower altitude, or when it is desired to decrease the maximum available pressure output supplied to the'brakes, the plate I45 will be adjusted downwardly by the screw I3I until it contacts with the diaphragm I3il or until, by further adjustment, it compresses the spring I5I to the point desired. Of course, when the apparatus is being operated to apply pressure to the brakes, the incoming air will in any case pass through the air inlet I42, ports I35, passage I49 and thence into the tube I21, thus applying to the diaphragm I39 a degree of vacuum exist- It will be understood that instead of supplying a vacuum to the fitting 4| this may be a vent and that instead of the port I05 being a vent this may be connected to a source of superatmospheric air pressure.

While I have described my invention above indetail I wish it to be understood that manychanges may be made therein without departing-j from the "spirit of the same.

I claim: 1. A compensator valve having a located in said chamber, having a valve element thereon, means for urging thesaid element to open position, another valve element movable with regard to said first mentioned element and having a reaction pressure area in said chamber to move the said other valve element in a direction towards closure against said first mentioned valve element when there is an increase of pressure in said chamber above said inlet pressure,

and a stop for one of said valve elements whereby thereon, means for urging the said element tov open position, another valve element, mounted so as to be movable on said plunger, movable with regard to said first mentioned element and having a reaction pressure area in said chamber to move the said other valve element in a direction towards closure against said first mentioned valve element when there is an increase of pressure in said chamber above said inlet pressure, and a stop on said enclosure for one ,of said valve elements whereby the first mentioned valve element can move away from said other valve element to open position, the said two valve elements having a passage between them so as to leave a passage around said first mentioned element when open.

3. A compensator valve having a liquid inlet, a valve enclosure having'an outlet chamber in communication with said inlet,'a piston valve plunger l. located in said chamber, having a valve element thereon, means for urging the said element to open position, another valve element movable with regard to said first mentioned element and having a reaction pressure area in said chamber to move the said other valve element in a direction towards closure against said first mentioned valve element when there is an increase of pressure in said chamber above said inlet pressure, and means whereby the first mentioned valve element can move away from said other valve element to open position, the said two valve elements having a passage between them so as to leavea passage past said first mentioned elementber in communication with said inlet, a piston valve plunger located in said chamber, having a valve element thereon, means for urging the saidelement to open position, another valve element movable with regard to said first mentioned element and having a reaction pressure area in said chamber to move the said other valve element in a direction towards closure against said first" mentioned valve element when there is anin liquid inlet, a valve enclosure having an outlet chamber in cornmunication with said inlet, a piston valve plunger ments having a passage between them so as to leave a passage around said first mentioned element when open, said valve plunger, when the valve is closed, having a larger area subject to the liquid in said inlet than the area subject to the liquid in said chamber.

5. A compensator valve having a liquid inlet, a valve enclosure having a hydraulic outlet chamber in communication with said inlet, a piston valve plunger located in said chamber, having a valve element thereon, means for urging the said element to open position, another valve element, mounted so as to be movable on said plunger, movable with regard to said first mentioned element and having a reaction pressure area in said chamber to move the said other valve element in a direction towards closure against said first mentioned valve element when there is an increase of pressure in said chamber above said inlet pressure, and a stop on said enclosure for one of said valve elements whereby the first mentioned valve element can move away from said other valve element to open position, the said two valve elements having a passage between them so as to leave a passage around said first mentioned element when open, said valve plunger,

.when the valve is closed, having a larger area subject to the liquid in said inlet than the area subject to the liquid in said chamber.

6. A compensator valve having a liquid inlet, a valve enclosure having a hydraulic outlet chamber in communication with said inlet, a piston valve plunger located in said chamber, having a valve element thereon, means for urging the said element to open position, another valve element, in the form of a sleeve around said plunger, having a liquid conduit therein and movable on said plunger, movable with regard to said first mentioned element and having a reaction pressure area in said chamber to move the said other valve 7 element in a direction towards closure against said first mentioned valve element when there is an increase of pressure in said chamber above said inlet pressure, and a stop on said enclosure for one of said valve elements whereby the first mentioned valve element can move away from said other valve element to open position, the said two valve elements having a passage between them so as to leave a passage around said first mentioned element when open, said valve plunger, when the valve is closed, having a larger area subject to the liquid in said inlet than the area subject to the liquid in said chamber.

'7. A compensator valve having a liquid inlet, a valve enclosure having a hydraulic outlet chamber in communication with said inlet, a piston valve plunger having a valve element thereon, means for urging the said element to open position, another valve element movable with regard to said first mentioned element and having a reaction pressure area in said chamber to move the said other valve element in a direction towards closure against said first mentioned valve element when there is an increase of pressure in said chamber above said inlet pressure, and means whereby the first mentioned valve element can move away from said other valve element to open position, the said two valve elements having a passage between them so as to leave a passage past said first mentioned element when open, said valve plunger, when the valve is closed, having a larger area subject to the liquid in said inlet than the area subject to the liquid in said chamber.

8. A compensator valve having a liquid inlet, a valve enclosure having a hydraulic outlet chamber in communication with said inlet, a piston valve plunger having a valve element thereon, means for urging the said element to open position, another valve element, mounted so as to be movable on said plunger, movable with regard to said first mentioned element and having a reaction pressure area in said chamber to move the said other valve element in a direction towards closureagainst said first mentioned valve element when there is an increase of pressure in said chamber above said inlet pressure, and a stop on said enclosure for one of said valve elements whereby the first mentioned valve element can move away from said other valve element to open position, the said two valve elements having a passage between them so as to leave a passage past said first mentioned element when open, said valve plunger, when the valve is closed, having a larger area subject to the liquid in said inlet than the area subject to the liquid in said chamher.

9. A compensator valve having a liquid inlet, a valve enclosure having a hydraulic outlet chamber in communication with said inlet, a piston valve plunger having a valve element thereon, means for urging the said element to open position, another valve element, in the form of a sleeve around said plunger, having a liquid conduit therein and movable on said plunger, movable with regard to said first mentioned element and having a reaction pressure area in said chamber to move the said other valve element in a direction towards closure against said first mentioned valve element when there is an increase of pressure in said chamber above said inlet pressure, and a stop on said enclosure for one of said valve elements whereby the first mentioned valve element can move away from said other valve element to open position, the said two valve elements having a passage between them so as to leave a passage past said first mentioned element when open, said valve plunger, when the valve is closed, having a larger area subject to the liquid in said inlet than the area subject to the liquid in said chamber.

EDWARD A. ROCKWELL.

REFERENCES CITED The following references are of record in the file of this patent:

UNITED STATES PATENTS Number Name Date 531,666 Van Auken Jan. 1, 1895 969,803 Pollock Sept. 13, 1910 948,404 Webb Feb. 8, 1910 2,166,384 West July 18, 1939 2,260,492 Stelzer Oct. 28, 1941 FOREIGN PATENTS Number Country Date 673 Great Britain Feb. 16, 1881 

